In radio-based automatic meter reading (AMR) systems, many utility meter endpoints need to be read by each reader. This type of communications arrangement is known as a point-multipoint system. One challenge in the design and deployment of such systems is ensuring that each endpoint device can be read reliably and as often as needed to meet the utility's billing cycle and measurement granularity requirements. Some utilities may wish to obtain hourly reads, for example, to monitor usage patterns. Certain utility providers may need to obtain consumption data from a large numbers of meters within a certain time window to determine its total “day take” of each most recent 24-hour period, for example.
Traditionally, AMR systems have utilized one-way endpoint devices that periodically transmit their consumption and related information as a “bubble-up” event. This type of transmission is known as a one-way system because the endpoint sends only outbound communications and does not receive any commands or acknowledgements from the reader. For ordinary remote reads, the endpoint has no way of knowing if its transmission has been received or if it needs to re-transmit a failed communication. Likewise, in systems wherein a reader is only occasionally within communication range of an endpoint, one-way endpoints have no way of knowing when a reader is present. One-way systems are designed such that endpoint devices transmit their messages from once every several seconds to once per minute. Because messages are transmitted so frequently, their length must be kept short to conserve energy in battery-powered endpoints. In addition, messages are preferably kept short to reduce the likelihood that messages will collide. This latter challenge exists regardless of whether endpoints are battery or externally powered.
Other known AMR systems utilize 1.5-way or two-way endpoint devices. One-and-one-half-way and two-way endpoints operate in a listen mode for most of the time. Reads are accomplished by interrogating specific endpoint devices by the reader. Collisions are reduced because endpoints within a reader's communication range can be interrogated one-at-a-time. In a 1.5-way system, an endpoint responds to a wakeup tone from a reader by transmitting its consumption and related information. In a two-way system, endpoint devices are responsive to various additional commands from the reader that may specify what type of information an endpoint should transmit, and that may configure operating parameters of the endpoint. One drawback of these two-way systems is the need for endpoints to operate in a receive mode (either frequently or continuously) in order to detect an interrogation signal or other command from the reader.
Another drawback of interrogation-based 1.5-way or two-way AMR systems is their incompatibility with the one-way systems described above, which are widely deployed. A simple one-way endpoint cannot detect or respond to an interrogation signal. Also, in areas where there might be simple one-way endpoints near interrogation mode endpoints, transmissions from the one-way endpoint would not be coordinated with those of the interrogation mode endpoints, resulting in an increased likelihood of message collisions. To date, no practical solution has been proposed that takes advantage of the power savings, backwards compatibility, and the other advantages of bubble-up systems, while enabling the more advanced functionality and remote configurability of interrogation mode systems.
Various AMR systems utilize hand-held readers and programming devices, vehicle-mounted readers, fixed location readers, and combinations thereof. Endpoints and readers among these different systems are preferably operated with different time periods between communication attempts, and different transmission power levels. As the size of a utility provider's customer base increases, the utility will tend to migrate from utilizing handheld readers to vehicle-based readers, and eventually to fixed reader systems. One challenge associated with making such a migration is the difficulty in re-configuring the AMR system devices to adjust their cooperating mode. Therefore, migration involves a substantial investment, not only in infrastructure upgrades, but in field labor.